Silicon nanoparticles (Si-NPs) capable of photoluminescence (PL) over the energy range from 790 nm to 900 nm were synthesized from silicon monoxide by increasing annealing temperatures from 25 degrees C to 950 degrees C. The PL of nanoparticles has remained stable for more than ten months from the date of the hydrosilylation of their surface by 1-octadecene. Solid samples of Si-NPs grafted with 1-octadecene are stable in the air up to 220 degrees C. The mean sizes of particles and their size distribution density function were derived from SAXS and XRD experiments and compared with TEM and HRTEM images and values calculated by the quantum limit model in accordance with the experimental optical absorption gap values. The absorption spectra of Si-NPs synthesized at 25 degrees C, 200 degrees C and 300 degrees C exhibited a blue shift of the fundamental absorption edge with respect to silicon single crystals; the absorption of Si600 and Si950 at the same incident photon shows energies increase. The PL peak of Si-NPs shifted toward longer waves as the synthesis temperature increased and exhibited a stronger red shift with respect to the photoexcitation wavelength. An analysis of the red shift led us to conclude that the surface states related to (Si-O) bonds influenced the effectiveness of PL. The Si-NPs PL quantum yield increased as the annealing temperature grew and reached a maximum of similar to 12% for Si-NPs at 950 degrees C. (C) 2011 Elsevier B. V. All rights reserved.